MediumChemistryHigh School (11–12)The d- and f-Block Elements › Lanthanoids and Actinoids (f-Block)NumericalConceptualA-Level IB NEET

A nucleus of uranium-238 (atomic number 92) absorbs a neutron…

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Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A nucleus of uranium-238 (atomic number 92) absorbs a neutron. The new nucleus then emits two beta particles, one after the other. Find the mass number of the final nucleus, its atomic number and the atomic number after the first beta emission. Name the final element.

Need a reminder? The key ideaShow

The actinoids fill 5f. All are radioactive. In each half-life, half of the sample decays: $m = m_0 \times 0.5^{t/t_{1/2}}$ . In a nuclear equation the mass numbers add up on both sides, and so do the atomic numbers. A beta emission raises the atomic number by one and leaves the mass number unchanged.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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